When talking about a computer, is it better to say:
"it's hooked up to many information data banks"
"it's hooked onto many etc..."?
Thank you
As far as I know, it's the first one.

That's what i would use.
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Me too.
I have also heard 'hooked-in to', but I think it's less common.
True, I've heard that too, but as you said, it's not as common.